None.
The present invention relates to a tire testing apparatus used to measure tire uniformity and load wheel alignment. More particularly, the present invention relates to such an apparatus having a sensor assembly for measuring the angular velocity of the road wheel. Most particularly, the present invention relates to such an apparatus having non-visible indicia on the surface of the load wheel and a sensor for detecting the indicia as the tire rotates.
Tire uniformity machines are used to test tires for quality and to repair minor detected defects in the tire. Uniformity machines employ a load wheel in contact with the test tire. Contact between the load wheel and the tire conveys information concerning the tire""s structural characteristics to a plurality of sensors mounted within the load wheel. Apart from the load wheel sensors, optical sensors measure the surface of the tire, tire velocity, and tire and load wheel alignment.
Known-optical sensors used to measure the angular or rotational velocity of the load wheel employ drums or discs containing visible graduations, which typically reflect or block light. The optical sensor detects the passage of these graduations and translates them into rotational velocity. The discs or drums can add substantial weight to the load wheel increasing the load on the load wheel drive motor and further change the inertia and dynamic balance of the load wheel itself, which may affect the load wheel""s response to the test tire.
As a further disadvantage, when defects, such as protrusions or other structural irregularities in the tire, are detected grinding elements located about the tire are used to remove or even out these defects. As can be appreciated, the grinders generate large quantities of tire particulate. These particles are suspended to an extent by their initial momentum and air currents generated by the tire, load wheel, and grinders. The suspended particulate interferes with the optical sensors interrupting the optical path between the sensor and the tire. Further, the grinding process heats the rubber particles making them tacky. In some instances, the tacky particles adhere to the optical sensors and can occlude the sensor optics. More commonly, these tacky particles fall onto the disc or drum and adhere to its surface covering the encoder""s graduations making them difficult or impossible to detect. As will be readily appreciated, any interruption of the sensor""s ability to detect these gradations results in inaccurate measurement of the rotational velocity.
A further disadvantage of optical sensors is the very small gap of about 0.004 inches between the rotating scale and the fixed sensors. This increases the potential for contact between the members resulting in permanent damage to the scale or the sensor.
Therefore, a need exists for an encoder that does not rely on optical sensors to measure tire and load wheel characteristics in a uniformity machine. A separate need exists for an encoder that measures the rotational velocity of the load wheel near its surface.
At least one object of the present invention, therefore, is to provide a road wheel reader that does not rely on optical sensors to measure load wheel angular velocity in a uniformity machine.
Another object of the present invention is to provide such a reader having a sensor for detecting magnetic particles carried on the surface of the load wheel, wherein the magnetic particles are spaced at regular intervals generating a series of pulses which the sensor uses to measure the tire surface characteristics.
In furtherance of at least one of these objects, the present invention provides a tire uniformity machine having a load wheel rotatably mounted within a frame, the tire uniformity machine including non-visible indicia adjacent the load wheel, and a sensor operatively located with respect to the indicia, wherein the sensor detects the presence of the indicia during the rotation of the load wheel.
The present invention further provides in a tire uniformity machine having a load wheel, an encoder assembly including a plurality of non-visible indicia carried by the load wheel and a sensor for detecting the indicia, wherein the sensor is in communication with a processor.
The present invention further provides in a tire uniformity machine having a load wheel and a processor, an encoder including a magnetic tape carried on an outer surface of the load wheel and axially located proximate the edge of the load wheel and a sensor operatively located with respect to the tape, the sensor communicating with the processor.
Accordingly, production of an improved road wheel reader of the character described becomes the principal object of this invention with other objects thereof becoming more apparent upon a reading of the following brief specifications, considered and interpreted in view of the accompanying drawings.